High-temperature circuits

ABSTRACT

Methods and systems for operating integrated circuits at temperatures higher than expected ambient temperatures. The heating may be of entire circuit boards, portions of the circuit boards (such as the components within a multiple-chip module) and/or single devices. Methods and related systems may be used in any high temperature environment such as downhole logging tools, and the devices so heated are preferably of silicon on insulator semiconductor technology.

CROSS-REFERENCE TO RELATED APPLICATIONS

None

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The various embodiments of the present invention are directed to hightemperature circuits for use in high temperature environments. Moreparticularly, at least some embodiments of the invention are directed tohigh temperature circuits for use in downhole logging tools.

2. Background of the Invention

In the exploration for and extraction of subterranean hydrocarbons,downhole tools are used to determine characteristics of formationstraversed by a borehole. In some cases, the downhole tools may bewireline tools which are suspended in a borehole after the drill stringhas been removed or “tripped.” In other cases, the downhole tools maycomprise measuring-while-drilling (MWD) and logging-while-drilling (LWD)tools coupled within the drill string.

Regardless of the mechanism by which a downhole tool is placed within aborehole, the range of temperatures within which the tool must operatemay vary widely. For example, a downhole tool placed within a boreholemay experience an ambient temperature of approximately 20° C. near thesurface, and at depth experience temperatures as high as or exceeding200° C. Because many of these downhole tools, especially MWD and LWDtools, have onboard electronics which may be semiconductor devices,these semiconductor devices need to be operable over the wide range oftemperatures.

Many commercially available semiconductor devices do not operateproperly in ambient conditions approaching or exceeding 200° C. Even ifa semiconductor device is operational at high temperature, its operatingcharacteristics may change with temperature. For example, logic gatesmay experience a significant change in the gate delay associated withsignal propagation through the gates. Amplifier gain may change as afunction of ambient temperature. Charged cell-type memory devices maylose their storage charge more quickly, thus requiring more frequentrefresh cycles. While it may be possible to cool downhole devices to bewithin the normal operating ranges, the implementation of downholecooling is difficult and extremely inefficient.

Thus, downhole tool manufacturers are relegated to testing the out ofspecification operating characteristics of commercially availablesemiconductor devices, using only those devices that still operate inthe out of specification temperature conditions, and compensating forchanges in operating characteristics caused by excessive temperatureswings.

SUMMARY OF SOME OF THE PREFERRED EMBODIMENTS

The problems noted above are solved in large part by a method andrelated system that controls the temperature of an electronic device, orgroup of electronic devices, to be above the expected ambienttemperature. One of the exemplary embodiments may be a method comprisingplacing a downhole tool within a borehole proximate to an earthformation (the downhole tool comprising an electronic circuit board),and maintaining at least a portion of the set of components on theelectronic circuit board at a predetermined temperature in excess ofexpected downhole temperatures. Some embodiments may involve placing adownhole tool having a silicon on sapphire integrated circuit in the setof components maintained at the predetermined temperature.

Other exemplary embodiments may comprise a downhole tool that has a toolbody (configured for placement within a borehole), and an electroniccircuit board coupled within the tool body (the electronic circuit boardcomprising a plurality of electronic components). In these embodimentsat least a portion of the electronic components on the electroniccircuit board are maintained at a predetermined temperature above thehighest temperature expected to be encountered by the downhole toolwithin the borehole.

The disclosed devices and methods comprise a combination of features andadvantages which enable it to overcome the deficiencies of the prior artdevices. The various characteristics described above, as well as otherfeatures, will be readily apparent to those skilled in the art uponreading the following detailed description, and by referring to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of the preferred embodiments of theinvention, reference will now be made to the accompanying drawings inwhich:

FIG. 1 illustrates a downhole tool within a borehole;

FIG. 2 illustrates a heated flask;

FIG. 3 illustrates a cutaway side view of at least some embodiments ofthe heated flask;

FIG. 4 illustrates a cutaway perspective view of a multiple-chip module;

FIG. 5 illustrates an elevational cutaway view of the multiple-chipmodule;

FIG. 6 illustrates a perspective view of the multiple-chip module with aheating element attached to a top surface thereof; and

FIG. 7 illustrates an overhead view of an integrated circuit inaccordance with at least some embodiments of the invention.

NOTATION AND NOMENCLATURE

Certain terms are used throughout the following description and claimsto refer to particular system components. This document does not intendto distinguish between components that differ in name but not function.

In the following discussion and in the claims, the terms “including” and“comprising” are used in an open-ended fashion, and thus should beinterpreted to mean “including, but not limited to . . . ”. Also, theterm “couple” or “couples” is intended to mean either an indirect ordirect electrical connection. Thus, if a first device couples to asecond device, that connection may be through a direct electricalconnection, or through an indirect electrical connection via otherdevices and connections.

The term “integrated circuit” refers to a semiconductor based component,or a group of components, designed to perform a specific task. In itsinitial stages, an integrated circuit may take the form of asubstantially circular disk or “wafer” upon which various layers areconstructed to implement the desired functionality. A “singulatedintegrated circuit” refers to a single component or group of componentscreated on a wafer using semiconductor technology, but wherein theindividual component or group of components has been cut (singulated)from the wafer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the various inventions were developed in the context ofdownhole logging and measuring tools. Because of this developmentalcontext, the following description relates to downhole logging tools.However, the systems and methods are equally applicable to othersituations where high ambient temperature is expected, and therefore thedescription should not be read as limiting the scope of the disclosureto just downhole logging tools.

FIG. 1 illustrates a downhole tool 10 constructed in accordance withembodiments of the invention. In particular, downhole tool 10 maycomprise a tool body 8 disposed within a borehole 12 beneath the surface14 of the earth. Tool 10 may be, for example, a measuring-while-drilling(MWD) or logging-while-drilling (LWD) tool coupled within a drillstring. Alternatively, tool 10 may be a wireline-type tool, suspended inthe borehole by way of an armored multi-conductor cable (not shown).Regardless of the precise mechanism by which the tool 10 is placed andheld within the borehole 12, the downhole tool may comprise anelectronic circuit board 16. Because the electronic circuit board 16 isintegral with the tool 10, the components on the electronic circuitboard 16 may experience a significant range of temperatures (e.g., from20° C. at the surface to 200° C. at depth). The precise nature of theelectronic circuit board 16 may vary depending upon the type of downholetool 10. If the downhole tool 10 is an exemplary electromagnetic waveresistivity (EWR) tool, the electronic circuit board 16 may comprisecomponents to implement signal generators, amplifiers and receivers. Ifthe downhole tool 10 is an exemplary neutron or gamma tool, theelectronic circuit board 16 may comprise components to implement controlof the neutron and/or gamma source, and neutron/gamma detectioncircuits.

In accordance with embodiments of the invention, at least a portion ofthe components on the electronic circuit board 16 may be heated to atemperature higher than the expected downhole temperature. In this way,variation in operation characteristics of semiconductor devices may bereduced. The following paragraphs describe various embodiments forcontrolling the temperature of at least a portion of the components onthe electronic circuit board 16.

FIG. 2 illustrates embodiments where the electronic circuit board 16 maybe placed within a sealed, possibly metallic, container 18 (which mayalso be known as a “flask”). Electrical signals may couple to and fromthe electrical components in the flask by way of a connector 19. In theembodiments illustrated in FIG. 2, components of the electronic circuitboard 16 in the flask 18 may be heated to the predetermined temperature.In some embodiments, heating the flask 18 may be by way of a heatingelement 20 coupled to an outside portion of the flask 18. In otherembodiments, the heating element may be within the flask 18. FIG. 3illustrates a cut-away side view of the flask 18 showing an exemplaryelectronic circuit board 16 having various components 24 mountedthereon. In the alternative embodiments, a heating element 26 (possiblya resistive heater) may be placed within the flask. The temperaturewithin the flask 18 may be controlled to the desired temperature, asmeasured by a temperature sensing device 25, which could be athermocouple or resistive thermal device (RTD).

Although it may be possible to control the temperature of all theelectrical components in a downhole tool to be greater than expecteddownhole temperatures, there may be some components whose operatingcharacteristics may change little with temperature, or may change insuch a way that does not affect operation. For this reason, inalternative embodiments of the invention only a portion of theelectrical components within a downhole tool 10 may be temperaturecontrolled. The manner in which the temperature of a component iscontrolled may be a function of a number of components for whichtemperature control is desired. In some embodiments, only a portion ofthe total electronic components for the downhole tool 10 may be placedwithin a flask, and only that portion heated in the manner as discussedwith respect to FIGS. 2 and 3. In yet further alternative embodiments ofthe invention, a plurality of components may be combined into a singlepackaged semiconductor device, such as a multiple chip module (MCM), andthe components within the module may be temperature controlled.

FIG. 4 illustrates a MCM 28 in accordance with various embodiments ofthe invention. In particular, FIG. 4 shows the MCM 28 having a partialcut-a-way to expose components therein. In at least some embodiments ofthe invention, integrated circuits singulated from a wafer may be used.FIG. 4 illustrates three such singulated semiconductor dies 30, 32 and34 enveloped in an encapsulant 29. The encapsulant 29, possibly in theform of an epoxy based material, may completely fill the space betweenthe components, or the encapsulant may be a small box within which theelectrical components 30, 32 and 34 are housed. Within the MCM 28,electrical conductors may couple the various components 30, 32 and 34 sothat the MCM 28 performs a desired task. Moreover, some or all of theintegrated circuits 30, 32 and 34 may also couple to external pins ofvarious construction. The exemplary MCM 28 of FIG. 4 illustrates twotypes of external pins through which the internal devices maycommunicate with external devices. In particular, a plurality of leads36 are illustrated on one edge of the MCM 28. In embodiments havingleads such as 36, a corresponding set of leads may be present on theopposite side of the module, and thus the MCM 28 would couple to aprinted circuit board in a fashion similar to dual in-line packageproducts. FIG. 4 also illustrates a packaging technique by showing theplurality of leads 38. Leads 38 as illustrated may be utilized in aquadrant package (quad pack) construction. In quad pack construction,the exemplary leads 38 may extend from all four of the sides (notspecifically shown in FIG. 4). Other mechanisms may be used toelectrically couple external devices to the integrated circuits withinthe MCM 28, such as a pin grid array.

Regardless of the precise mechanism by which components in a multi-chipmodule couple to external devices, in accordance with embodiments of theinvention an individual MCM 28 may be temperature controlled to holdcomponents internal to the MCM 28 at temperatures above expected ambienttemperatures.

FIG. 5 illustrates a cross-sectional view of a multi-chip moduleconstructed in accordance with embodiments of the invention. The MCM 28illustrated in FIG. 5 is shown to have a pin grid array 42 as theexternal mechanism by which components within the module couple toexternal devices; however, the pin grid array 42 is only exemplary. FIG.5 also illustrates that, in accordance with embodiments of theinvention, the multi-chip module 28 may comprise an internal heatingelement 52, such as a resistive heater, and a temperature sensing device50, such as an RTD. A temperature control circuit, which may eitherinternal or external to the MCM 28, may control the flow of electricalcurrent through the heating element 52 such that the components withinthe MCM 28 may be operated at a predetermined temperature. For example,electrical component 30 may be an integrated circuit specificallydesigned or configured for temperature control applications. Aspreviously mentioned, the temperature at which the various componentsare held is preferably a temperature above the expected ambienttemperature. In the exemplary case of use in downhole tools, it isanticipated that the heating element 52 may hold the internal componentsof the MCM 28 at approximately 220° C., which is above the highestexpected ambient temperature for most downhole applications of 200° C.In situations where the highest expected ambient temperature may belower than 200° C., the temperature at which the resistive elementmaintains the components within the multi-chip module 28 may likewise belower.

FIG. 6 illustrates embodiments of the MCM 28 utilizing an externalheating element 54, in this case coupled to a top surface of the MCM 28.The electrical circuit that controls the heater 54 may be eitherinternal to the multi-chip module 28, or may be external to the MCM 28.In the case of an external circuit, the multi-chip module 28 maynone-the-less have an internal temperature sensing device, such asthermal couple or RTD, to measure the internal temperature for controlpurposes.

The embodiments of the invention described to this point involve the useof multiple singulated integrated circuits, such as 30, 32 and 34illustrated in FIG. 4. However, the various heating techniques may alsobe used when only one singulated integrated circuit is packaged tobecome a packaged semiconductor device. In situations where only onesingulated integrated circuit is used, it may be possible to integrateone or both of the temperature sensing device and the heating elementwithin the integrated circuit device itself. FIG. 7 shows an overheadview of a singulated integrated circuit device in accordance withalternative embodiments of the invention. In particular, one or moreelectrical components may be built into the region 70. The one or morecomponents in region 70 may implement functionality such as anoperational amplifier, a digital logic gate, a receiver circuit, and thelike. Constructed on the same integrated circuit may be a heatingelement 72. FIG. 7 illustrates that the heating element 72 may be formedaround the periphery of the electrical component(s) in region 70.However, placement around the periphery is only exemplary, and theheating elements may be dispersed above, below and/or within theelectrical component(s) in region 70. In accordance with embodiments ofthe invention, electrical current may be selectively allowed to flowthrough the heating element 72, which may simply be a resistive heater,to control the temperature of the electrical component(s) in region 70.The integrated circuit in accordance with these alternative embodimentsmay also comprise a temperature sensing device 74 in operationalrelationship to the one or more electrical components in region 70. Asillustrated in FIG. 7, the temperature sensing device 74, which may anRTD, is centered within region 70; however, placement of the temperaturesensing device 74 is not critical, and may be anywhere on the footprintof the integrated circuit. In some embodiments, a temperature controlcircuit 76 may be integrated among the one or more electrical componentsin region 70. The temperature control circuit 76 may read thetemperature of the integrated circuit using the temperature sensingdevice 74, and then selectively control the flow of electrical currentthrough the heating element 72.

In accordance with embodiments of the invention, the integrated circuitswhich are heated to controlled temperatures above expected ambienttemperatures are preferably based on silicon on insulator (SOI)technology. As the name implies, the silicon on insulator technology isuses silicon films grown or deposited on insulating substrates. Thesilicon film may be masked, etched and doped to create components, suchas transistors, diodes, resistors and capacitors, which components incombination perform desired functions. By manufacturing the integratedcircuits onto an insulating substrate, the effects of high temperatureoperation, such as leakage current through the substrate, may be reducedso that the high temperature operation does not severely and/oradversely affect operation. The insulator upon which the components areconstructed may be any suitable insulator, such as sapphire and spinel.Thus, the integrated circuits having internal or external heatingelement illustrated in FIGS. 1-7 above are preferably constructed, atleast in part, using integrated circuits based on the silicon oninsulator, and in particular silicon on sapphire, construction.

The above discussion is meant to be illustrative of the principles andvarious embodiments of the present invention. Numerous variations andmodifications will become apparent to those skilled in the art once theabove disclosure is fully appreciated. It is intended that the followingclaims be interpreted to embrace all such variations and modifications.

1. A method comprising: placing a downhole tool within a boreholeproximate to an earth formation, the downhole tool comprising anelectronic circuit board; and maintaining at least a portion of a set ofcomponents on the electronic circuit board at a predeterminedtemperature in excess of expected downhole temperatures.
 2. The methodas defined in claim 1 wherein maintaining further comprises maintainingthe predetermined temperature by operating the set of components withina heated flask.
 3. The method as defined in claim 2 further comprisingheating the flask by way of a heating element coupled to an exteriorsurface of the flask.
 4. The method as defined in claim 2 furthercomprising heating the flask by way of a heating element disposed withinthe flask.
 5. The method as defined in claim 1 wherein maintainingfurther comprises maintaining a multiple-chip module comprising the setof components at the predetermined temperature.
 6. The method as definedin claim 5 wherein maintaining the multiple-chip module at thepredetermined temperature further comprises heating the multiple-chipmodule with a heating element coupled to an exterior surface of themultiple chip module.
 7. The method as defined in claim 5 whereinmaintaining the multiple-chip module at the predetermined temperaturefurther comprises heating the multiple-chip module with a heatingelement disposed within the multiple chip module.
 8. The method asdefined in claim 5 further comprising controlling temperature by atemperature control circuit disposed within the multiple-chip module. 9.The method as defined in claim 1 further comprising: wherein placingfurther comprises placing the downhole tool having a silicon on sapphireintegrated circuit on the electronic circuit board; and whereinmaintaining further comprises maintaining the silicon on sapphireintegrated circuit device at the predetermined temperature.
 10. Adownhole tool comprising: a downhole tool body; and an electroniccircuit board coupled to the tool body, the electronic circuit boardcomprising a plurality of electronic components; wherein at least aportion of the plurality of electronic components are maintained at apredetermined temperature above the highest temperature in the borehole.11. The downhole tool as defined in claim 10 further comprising a flaskenveloping the electronic circuit board, and wherein the temperaturewithin the flask is maintained at the predetermined temperature.
 12. Thedownhole tool as defined in claim 11 wherein the flask further comprisesa heating element.
 13. The downhole tool as defined in claim 12 whereinthe heating element is coupled to the exterior of the flask.
 14. Thedownhole tool as defined in claim 12 wherein the heating element isinside the flask.
 15. The downhole tool as defined in claim 10 whereinthe electronic circuit board further comprises a multiple-chip modulehousing at least a portion of the electronic components, and wherein themultiple-chip module is maintained at the predetermined temperature. 16.The downhole tool as defined in claim 15 wherein the multiple-chipmodule further comprises a heating element disposed within themultiple-chip module, and wherein the heating element maintains themultiple-chip module at the predetermined temperature.
 17. The downholetool as defined in claim 15 further comprising a heating element coupledto an exterior surface of the multiple-chip module, and wherein theheating element maintains the multiple-chip module at the predeterminedtemperature.
 18. The downhole tool as defined in claim 10 wherein atleast a portion of the electronic components comprise devicesconstructed as silicon on insulator.
 19. The downhole tool as defined inclaim 18 wherein the insulator is sapphire.
 20. A method of making apackaged semiconductor device, the method comprising: placing asingulated integrated circuit within an encapsulant; and mechanicallycoupling a heating element to the encapsulant.
 21. The method as definedin claim 20 wherein placing further comprising placing a plurality ofsingulated integrated circuits within the encapsulant.
 22. The method asdefined in claim 21 wherein placing further comprises placing aplurality of singulated integrated circuits wherein at least one of theplurality of singulated integrated circuits is a temperature controlcircuit.
 23. The method as defined in claim 20 wherein coupling furthercomprises mechanically coupling the heating element to an exteriorsurface of the encapsulant.
 24. The method as defined in claim 20wherein coupling further comprises placing the heating element withinthe encapsulant.
 25. The method as defined in claim 20 wherein placingfurther comprises placing a silicon on insulator integrated circuitwithin the encapsulant.
 26. The method as defined in claim 25 whereinplacing further comprises placing a silicon on sapphire integratedcircuit within the encapsulant.
 27. A system comprising: a singulatedintegrated circuit; an encapsulant enveloping the singulated integratedcircuit; and a heating element coupled to the encapsulant; wherein theheating element maintains the temperature of the singulated integratedcircuit at a predetermined temperature in excess of the highest expectedambient temperature.
 28. The system as defined in claim 27 farthercomprising a plurality of singulated integrated circuits enveloped bythe encapsulant.
 29. The system as defined in claim 27 wherein theheating element is disposed within the encapsulant.
 30. The system asdefined in claim 27 wherein the heating element is coupled to an outersurface of the encapsulant.
 31. The system as defined in claim 27further comprising: a temperature control circuit within theencapsulant; and a temperature sensing device coupled to the temperaturecontrol circuit and in operational relationship to the singulatedintegrated circuit die; wherein the temperature control circuit controlsthe power provided to the heating element responsive to a temperaturesensed by the temperature sensing device.
 32. The system as defined inclaim 31 wherein the temperature control circuit is integrated on thesingulated integrated circuit.
 33. The system as defined in claim 31wherein the temperature sensing device is integrated on the singulatedintegrated circuit.
 34. The system as defined in claim 33 wherein thetemperature sensing device further comprises a resistive thermal device(RTD).
 35. The system as defined in claim 27 wherein the singulatedintegrated circuit further comprises a singulated integrated circuitconstructed as silicon on sapphire.
 36. A method comprising:constructing an electrical component on a silicon on insulatorsubstrate; constructing a heating element proximate to the electricalcomponent on the silicon on insulator substrate; and constructing atemperature sensing device proximate to the electrical component on thesilicon on insulator substrate.
 37. The method as defined in claim 36wherein constructing the electrical component further comprisesconstructing the electrical component on a silicon on sapphiresubstrate.
 38. The method as defined in claim 36 further comprisingconstructing a temperature control circuit on the silicon on insulatorsubstrate, the temperature control circuit electrically coupled to thetemperature sensing device, and wherein the temperature control circuitis configured to control electrical current flow through the heatingtrace to control the temperature of the electrical component.
 39. Asemiconductor device comprising: an electrical component constructed ona silicon film, the silicon film on an insulating substrate; atemperature sensing device constructed on the silicon film; and aresistive heating element constructed on the silicon film; wherein theresistive heating element heats the electrical component responsive tothe temperature sensed by the temperature sensing device.
 40. Thesemiconductor device as defined in claim 39 further comprising atemperature control circuit coupled to the temperature sensing device,and wherein the temperature control circuit controls the electricalcurrent flow through the resistive heating element responsive to thetemperature sensed by the temperature sensing device.
 41. Thesemiconductor device as defined in claim 40 wherein the temperaturecontrol circuit commands an external switch to control the electricalcurrent flow through the resistive heating element.
 42. Thesemiconductor device as defined in claim 40 further comprising a powerflow control circuit coupled to the temperature control circuit and theresistive heating trace, and wherein the temperature control circuitasserts a signal to the power flow control circuit to control theelectrical current flow through the resistive heating element.
 43. Thedevice as defined in claim 39 wherein the insulating substrate issapphire.